Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$166.55	13.825%	$189.5755	$189.58	$189.60	$189.60
Purchase #2	$160.72	7.538%	$172.8351	$172.84	$172.85	$172.80
Purchase #3	$104.61	5.650%	$110.5205	$110.52	$110.50	$110.50
Purchase #4	$49.79	8.290%	$53.9176	$53.92	$53.90	$53.90
Purchase #5	$131.37	4.859%	$137.7533	$137.75	$137.75	$137.80
Purchase #6	$94.64	5.125%	$99.4903	$99.49	$99.50	$99.50
Purchase #7	$229.41	13.110%	$259.4857	$259.49	$259.50	$259.50
7 purchase totals =	$937.09		$1,023.5780	$1,023.59	$1,023.60	$1,023.60